The long-term objective of our work is to understand the role of Ca and energy metabolism in cardiac failure. Such an understanding is critical to the design of effective interventions for its treatment. Our strategy is to investigate the role of these factors in failure at the cellular level, using isolated ventricular cells. We have developed a procedure for isolating Ca-tolerant cells from adult rat hearts. From experimental results published over the past few years, we have established that the cells have metabolic and functional properties similar to those of cells in the whole heart. The yield of such cells, however, is only about one quarter of the original myocytes. Our first aim is to gain further insight into the determinants of cell survival and so improve our isolation methodology to give greater yield. The second aim is to use a procedure similar to that established for rat cells to isolate Ca-tolerant cells from human heart tissue, and to determine the contractile functional properties of single cells in collaboration with Dr. Richard Moss in the Department of Physiology. This will involve attachment of single cells to a force transducer, to permit measurement of force velocity curves, length-tension relations, treppe, and power output. Cells from normal dog hearts will be examined first. Then we will characterize cells from human cardiomyopathic hearts and hearts with end-stage ischemic disease made available through the heart transplant program in the Department of Surgery, along with any normal donor hearts which for technical reasons cannot be transplanted. This will be a unique opportunity to determine for the first time the contractile properties of failing human ventricular tissue at the cellular level. We will also seek to develop a method for isolating Ca-tolerant cells from human heart tissue pieces that cannot be perfused, and to define their contractile properties. Cells from tissue removed during left ventricular aneurysm repair and surgical correction of idiopathic hypertrophic subaortic stenosis will be examined, as well as cells from normal right ventricular tissue pieces removed during correction of Tetralogy of Fallot. The contractile properties of cells from normal and cardiomyopathic hamster hearts will also be measured. Finally, in studies with cells from rat hearts, we will continue to investigate the role of Ca and energy metabolism in cell pathophysiology, with a view to developing increasingly discriminating functional tests for application to isolated human heart cells.